The present invention relates to lightning protection apparatus for an exterior structural surface, either an electrically conductive or a non-conductive surface, and finds particular utility in providing lightning protection for aerospace vehicles. In the field of aerospace vehicles, there exists a need for a lightning protection apparatus which will reduce interior sparking and minimize structural damage to the airfoil surface. There is also a need for an apparatus which will reduce the time that a lightning stroke is attached to the surface of a vehicle.
Exterior surfaces of vehicles such as an aircraft are frequently coated with paints that have excellent dielectric strength properties; that is, the paint coatings have the ability to resist puncture by a lightning stroke. However, when a puncture does occur at a weak point in the paint coating the lightning stroke makes contact with the conductive surface of the aircraft at a point referred to as the attachment point. All of the lightning energy may thus be concentrated at one point. This can produce severe skin surface damage, hot spots, skin puncture, and interior sparking at joints or fasteners.
There currently exist a number of conventional methods for providing lightning protection to painted surfaces. For example, the thickness of the conductive surface can be increased in order to prevent skin puncture, or conductive overlays can be provided over the existing painted surface. These methods are disadvantageous in that they add weigh to the aircraft and are costly. High dielectric strength barriers have been provided in order to prevent attachment to the surface. However, this method, in addition to adding weight and cost, cannot be relied upon for dielectric strength integrity. Another method that has been employed is to load the outer decorative layer of paint with fine conductive particles. However, this coating does not perform well mechanically in severe environments when applied over conductive surfaces and cannot be color matched with the normal decorative colors.
It is therefore an object of the present invention to provide a system of lightning protection for a conductive or nonlayer, which will minimize interior sparking and structural damage to the surface.
It is a further object of the present invention to provide a system of lightning protection which will not add excessive weight to the conductive surface.
It is still a further object of the present invention to provide a system of lightning protection for a conductive surfa which will perform well mechanically in severe environments and will have a pleasing appearance.
It is a further object of the present invention to provide a system of lightning protection which will reduce the time that a lightning stroke is attached to the conductive surface.